Modular converter

ABSTRACT

A converter for an electric motor or transformer, the converter being comprising a connection box having passages for electrical conductors and having a semiconductor electronic module removably fixed to the connection box. The electronic module has a radiator-forming box that is open at one end, at least one electronic card at least partially embedded in a resin cast inside said radiator-forming box, and at least one connector emerging from the resin. The opening of the radiator-forming box enables it to be fitted to the connection box. The connection box has at least one window giving access to the connector(s) of the electronic module.

[0001] The present invention relates to a converter for an electricmotor or a transformer and more particularly but not exclusively aconverter for a motor that is asynchronous or synchronous, that haspermanent magnets, or that operates on DC.

BACKGROUND OF THE INVENTION

[0002] The term “converter” is used to cover inverters and drives, i.e.any static semiconductor apparatus enabling an electric motor to becontrolled or frequency to be changed when feeding an electrictransformer.

[0003] Converters are known that comprise electronic cards received in abox fixed on the motor.

[0004] The drawback of such known converters is that in the event of anelectronic failure, it is necessary to replace the entire box, whichmeans that the box must be separated from the motor.

[0005] Furthermore, each box is specific to a given motor which givesrise to relatively high manufacturing costs when a motor is made in ashort manufacturing run only.

OBJECTS AND SUMMARY OF THE INVENTION

[0006] The invention seeks to provide a novel converter which makes itpossible in particular to replace faulty electronic cards easily.

[0007] Another object of the invention is to reduce the cost price ofthe converter.

[0008] The invention achieves this by the fact that the convertercomprises a connection box having passages for electrical conductors,and a semiconductor electronic module releasably fixed to the connectionbox, said electronic module comprising a radiator-forming box that isopen at one end, at least one electronic card that is at least partiallyembedded in a resin cast into the inside of said radiator-forming box,and at least one connector emerging from the resin, the opening of theradiator-forming box being arranged in such a manner as to enable it tobe fitted to the connection box, the connection box having at least onewindow giving access to the connector(s) of the electronic module.

[0009] By means of the invention, the electronic module of the convertercan easily be replaced without it being necessary to separate theconnection box from the electric motor or transformer on which it isfixed.

[0010] Furthermore, electrical connections can easily be established bythe user when the radiator-forming box and the connection box are fixedto each other by means of the access window provided in the connectionbox.

[0011] Furthermore, the fact that the electronic card(s) of theelectronic module is/are embedded in a resin cast into the inside of theradiator-forming box guarantees that the electronic module is reliableand electrically insulated.

[0012] Advantageously, the said resin is thermally conductive, so as toimprove dissipation of heat from the electronic module.

[0013] The invention also makes it possible to achieve savings of scalein the manufacture of the radiator-forming box and in the manufacture ofthe electronic cards it contains since it is the connection box whichserves as the interface and which needs to be fitted to different typesof motor.

[0014] In other words, it is possible to make different types ofconnection box all arranged to receive the same type of radiator-formingbox.

[0015] In a particular embodiment, the connection box includes means forfixing to a motor or a transformer.

[0016] Advantageously, the converter includes a thermally insulatinggasket at the interface between the radiator-forming box and theconnection box.

[0017] This insulating gasket ensures that when the motor is operatingat low speed so that its cooling fan is turning relatively slowly, theheat given off by the motor is not conducted to the electronic moduleand does not affect the operation thereof.

[0018] Advantageously, the electronic module has one or more electronicpower components mounted on the rear face of a card and in thermalcontact with the inside face of the rear wall of the radiator-formingbox.

[0019] Preferably, the inside face of the rear wall of theradiator-forming box has portions in relief arranged to co-operate withthe above-mentioned electronic power component(s) so as to facilitatepositioning of the electronic card(s) relative to the radiator-formingbox.

[0020] Advantageously, the electronic module has a card carrying atleast one connector for providing electric connection between theconverter and electric wires conveying control signals, and alsopreferably but not necessarily a connector for supplying power and aconnector for connection to the motor or the transformer.

[0021] Also advantageously, when the electronic module has a pluralityof electronic cards, most of the bulky components of the electronicmodule are mounted on those faces of the electronic cards which facetowards the middle of the radiator-forming box, thereby making itpossible for the structure to be more compact.

[0022] Advantageously, on at least one face, the radiator-forming boxhas fins in the form of discontinuous parallel ribs creating ranks ofribs in two mutually perpendicular directions, with air being able toflow between the fins in each of the two directions.

[0023] Disposing the fins in this way makes it possible to guaranteecooling by convection in two different orientations of the converterrelative to the vertical.

[0024] Each fin is preferably oblong in cross-section, with two oppositemain faces converging towards the tip of the fin.

[0025] This shape makes it easy to provide fins that are longer orshorter depending on the power to be dissipated.

[0026] The fins are advantageously made using a mold that has one ormore interchangeable slides that are selected depending on the length tobe given to the fins.

[0027] This avoids the need to use a special mold for making fins ofdifferent lengths, since the fins can be made to the desired length byselecting the appropriate slide(s).

[0028] In addition, the fins remain relatively short and they hardenquite quickly, thereby making high rates of throughput possible withinjection molding.

[0029] The invention also provides an electric machine, e.g. an electricmotor, including a converter as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other characteristics and advantages of the present inventionwill appear on reading the following detailed description ofnon-limiting embodiments, and on examining the accompanying drawings, inwhich:

[0031]FIG. 1 is a fragmentary and diagrammatic axial section view of aconverter of the invention;

[0032]FIG. 2 is a side view showing the cards of the electronic moduleon their own;

[0033]FIG. 3 is a plan view looking along arrow III of FIG. 2;

[0034]FIG. 4 is a diagrammatic and fragmentary view of the cooling finsmade on the rear face of the radiator-forming box; and

[0035]FIG. 5 shows a converter provided with wall-mounting tabs.

MORE DETAILED DESCRIPTION

[0036]FIG. 1 shows a converter of the invention, containing anelectronic module 10 of power lying in the range 0.25 kilowatts (kW) to15 kW, for example, and comprising a radiator-forming box 20 that isopen to the front and made by injection molding aluminum, the boxcontaining a set of electronic cards 30 constituted in this case by fourelectronic cards, namely a front card 31, a rear card 32, and twointermediate cards 33 and 34.

[0037]FIG. 2 shows the set of electronic cards 30 in isolation.

[0038] The front and rear cards 31 and 32 are parallel and perpendicularto the intermediate cards 33 and 34.

[0039] In the vicinity of their ends adjacent to the front and rearcards 31 and 32, the intermediate cards 33 and 34 are provided withslots, while the front and rear cards 31 and 32 are provided withconnection tongues shaped to engage in the above-mentioned slots.

[0040] The connection tongues of the front card 31 carry references 31 ato 31 d in FIG. 3.

[0041] Conductor tracks 35 are made on the connection tongues, saidtracks forming integral portions of the printed circuit of the card.

[0042] These conductor tracks are electrically connected to the printedcircuits of the cards that have slots.

[0043] Solder bridges 36 provide electrical continuity between thevarious cards 31 to 34 via the associated tongues and slots and alsoserve to prevent the cards from moving relative to one another.

[0044] The electrical circuit of the converter can thus be built withoutusing ribbons of conductor wires for interconnecting various cards,unlike the structure of conventional converters.

[0045] In the embodiment described, the front and rear cards 31 and 32have tongues for engaging in corresponding slots provided in theintermediate cards 33 and 34.

[0046] Naturally, it would not go beyond the ambit of the invention toprovide the intermediate cards 33 and 34 with tongues and the front andrear cards 31 and 32 with slots for receiving those tongues.

[0047] It is also possible to provide one of the intermediate cards 33and 34 with tongues and the other with slots.

[0048] In the embodiment described, the front card 31 has a connectorstrip 37 on its outside face 31 e, which strip enables the converter tobe connected to electric lines, e.g. conveying control signals to causethe motor to revolve more quickly or more slowly.

[0049] Electronic power components 38 are mounted on the rear face 32 aof the rear card 32.

[0050] These connector power components 38 are pressed against theinside face 21 a of the rear wall 21 of the radiator-forming box 20 soas to transfer heat thereto by conduction.

[0051] It will be observed on examining FIGS. 1 and 2 that a largefraction of the bulky components 58 of the converter are mounted onthose faces of the intermediate cards 33 and 34 that face towards thecenter of the radiator-forming box 20, thereby making it possible toprovide a converter that is particularly compact.

[0052] In the embodiment described, the converter has electric cables 39connected to one of the cards and extending out from theradiator-forming box 20.

[0053] A resin 40 that is electrically insulating but thermallyconductive is cast into the inside of the radiator-forming box 20 toprotect the set of electronic cards 30 from moisture and vibration, andalso to improve electrical insulation.

[0054] The resin 40 comes up to the level of the front card 31, as canbe seen in FIG. 1;

[0055] As shown, the inside face 21 a of the rear wall 21 of theradiator-forming box 20 has portions in relief 21 b for ensuring thatthe set of electronic cards 30 takes up a predetermined position insidethe radiator-forming box 20 before the resin 40 is cast.

[0056] These portions in relief 21 b are arranged to co-operate with theelectronic power components 38.

[0057] Advantageously, the radiator-forming box 20 has a plurality offins 50 on the outside face of its rear wall, which fins are showndiagrammatically in FIG. 4.

[0058] The fins 50 are not shown in FIG. 1 in order to clarify thedrawing.

[0059] The fins 50 are placed in parallel rows 51.

[0060] Within each row 51, the fins 50 are placed at regular intervalsso that they also make up column alignments 52 perpendicular to the rows51.

[0061] Each fin 50 is elongate in shape in a direction perpendicular tothe plane of the rear wall 21, and it has a cross-section that is oblongwith its long axis extending parallel to the direction of the rows 51.

[0062] On examining FIG. 4, it will be seen that air can flow betweentwo consecutive rows 51 and also between two consecutive columns 52,thereby enabling the converter to be installed either with its rows 51horizontal, in which case the radiator-forming box 20 is oriented asshown in FIG. 1, i.e. with its intermediate cards 33 and 34 horizontal,or else in a variant with the rows 51 vertical, in which case theintermediate cards 33 and 34 are vertical.

[0063] In either case, vertical convection flow of air between the fins50 is not impeded.

[0064] Each fin 50 has two opposite main plane faces 53 which convergeat an angle of a few degrees towards the free end of the fin.

[0065] Depending on the heat power to be dissipated, the fins 50 aremade to be longer or shorter.

[0066] In the example described, the fins 50 are integrally formed inthe same aluminum as the remainder of the box by using a mold which hasa rear slide that is interchangeable, thus making it possible to makelonger or shorter fins by selecting an appropriate slide.

[0067] Thus, a single mold can be used to make a box having fins of alength that matches the power it is to dissipate.

[0068] The generally flattened shape of each fin 50 makes the radiatoreasier to clean than conventional radiators having a plurality oftruncated cones since the plane main faces of the fins provide arelatively large contact area with a cleaning member that is movedparallel to the rows 51.

[0069] In the example of FIG. 1, the electronic module 10 is assembledwith an electrical connection box 60 fixed to the top portion of thecase of an electric motor (not shown).

[0070] The radiator-forming box 20 is positioned in such a manner as tolie in the flow of cooling air generated by the fan of the motor.

[0071] The connection box 60 has bolts 61 for fixing to the motor and italso has connection terminals 62 that are connected to the motor.

[0072] The wires 39 of the converter 10 are connected to theseconnection terminals 62.

[0073] In its top portion, the box 60 has a window 63 providing a userwith easy access to the electrical conductors 39, to the connectionterminals 62, and to the connector strip 37.

[0074] Passages having sealing gaskets are provided through the box 60in conventional manner to pass the power supply and control wires of theconverter 10.

[0075] These passages are not shown herein in order to clarify thedrawing.

[0076] In the embodiment described, the radiator-forming box 20 has afront flange 26 provided with a plurality of fixing screws 23 serving tomount it on the connection box 60.

[0077] A thermally insulating gasket 25 is placed around the flange 26so as to constitute a thermal barrier impeding the transmission of heatfrom the connection box 60 to the radiator-forming box 20.

[0078] This thermal barrier is particularly useful when the motor isoperating at low speeds, i.e. when the fan driven by the motor shaft isrevolving slowly.

[0079] The presence of the gasket 25 then slows down the transmission ofheat by conduction from the case of the motor to the radiator-formingbox 20.

[0080] The set of electronic cards 30 enables a module to be made whichcan be assembled to a connection box 60 fixed on a motor, as describedabove, or in a variant enables it to be received in an independent box,as described below with reference to FIG. 5.

[0081] In this figure, wall mounting tabs 70 are provided on the sidewalls of the box housing the set of electronic cards 30.

[0082] In a variant (not shown), these mounting tabs are provided on therear wall of said box.

[0083] An electrical connection box 80 is fixed on the front of the boxhousing the set of electronic cards 03;

[0084] Inlet and outlet cables 81 and 82 are shown connected to the setof electronic cards 30 inside the connection box 80.

[0085] If so required by the electrical power to be dissipated, theconverter box can have fins of the kind described with reference to FIG.4.

[0086] Naturally, the invention is not limited to the embodimentsdescribed above.

[0087] In particular, the set of electronic cards 30 could be made witha front card, a rear card, and only one intermediate card if the numberof electronic components does not require the use of a secondintermediate card.

[0088] The orientation of the cards relative to the walls of the boxcould also be modified.

[0089] An intermediate module could be interposed between the electricconnection box and the radiator-forming box, e.g. to dissipate heatenergy.

[0090] One or more electronic power components can be mounted on one ofthe intermediate cards and can be thermally connected to theradiator-forming box receiving the set of electronic cards.

[0091] The motor can be replaced by a transformer, e.g. a transformerhoused in the case of a motor having its primary and secondary windingswound on magnetic circuits analogous to those of a stator and of arotor.

1. A converter for an electric motor or transformer, the convertercomprising a connection box having passages for electrical conductors,and a semiconductor electronic module releasably fixed to the connectionbox, said electronic module comprising a radiator-forming box that isopen at one end, at least one electronic card that is at least partiallyembedded in a resin cast into the inside of said radiator-forming box,and at least one connector emerging from the resin, the opening of theradiator-forming box being arranged in such a manner as to enable it tobe fitted to the connection box, the connection box having at least onewindow giving access to the connector(s) of the electronic module.
 2. Aconverter according to claim 1 , wherein the connection box has mountingmeans enabling it to be mounted on a motor or a transformer.
 3. Aconverter according to claim 1 , including a thermally insulating gasketat the interface between the radiator-forming box and the connectionbox.
 4. A converter according to claim 1 , wherein the radiator-formingbox is placed in the flow of air generated by the cooling fan of anelectric motor on which the connection box is fixed.
 5. A converteraccording to claim 1 , wherein the resin is thermally conductive.
 6. Aconverter according to claim 1 , wherein the electronic module has oneor more electronic power components mounted on the rear face of a cardand in thermal contact with the inside face of the rear wall of theradiator-forming box.
 7. A converter according to claim 6 , wherein theinside face of the rear wall of the radiator-forming box has portions inrelief arranged to co-operate with the electronic power components(s).8. A converter according to claim 1 , wherein the electronic module hasa card carrying at least one connector for electrically connecting theconverter to electric wires conveying control signals and preferably aconnector for connection to a power supply and a connector forconnection to the motor or transformer.
 9. A converter according toclaim 1 , wherein the radiator-forming box has fins on at least oneface, the fins being in the form of discontinuous parallel ribsestablishing ranks of fins in two mutually perpendicular directions, airbeing able to flow between the fins in each of the two directions.
 10. Aconverter according to claim 9 , wherein each fin has a cross-sectionthat is oblong in shape, with two opposite main plane faces thatconverge towards a tip of the fin.
 11. A method of manufacturing aconverter having fins as defined in claim 10 , wherein the fins are madeusing a mold having one or more interchangeable slides that are selecteddepending on the length to be given to the fins.
 12. An electric machinesuch as an electric motor, including a converter as defined in claim 1 .